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Abstract:

A plasmon generator includes a first portion and a second portion. A core
of a waveguide includes a main body portion and a protruding portion. The
main body portion has a first surface and a second surface parallel to
each other. The protruding portion lies on the first surface. A cladding
of the waveguide includes a receiving-portion-forming layer lying on the
first surface. At least part of the first portion of the plasmon
generator is received in a receiving portion defined by the protruding
portion and the receiving-portion-forming layer.

Claims:

1. A near-field light generator comprising: a waveguide including a core
through which light propagates, and a cladding provided around the core;
and a plasmon generator, wherein the core has a first front end face
lying at an end of the core in a first direction, the first direction
being a direction of travel of the light propagating through the core,
the plasmon generator has a second front end face lying at an end of the
plasmon generator in the first direction, the core and the plasmon
generator are adjacent in a second direction orthogonal to the first
direction, the plasmon generator includes a first portion and a second
portion adjacent in the second direction, the second portion including
the second front end face, the core includes a main body portion and a
protruding portion adjacent in the second direction, the main body
portion has a first surface facing toward the plasmon generator, and a
second surface opposite to the first surface, the first surface and the
second surface being flat surfaces parallel to each other, the first
surface includes a first region, a second region and a third region, the
first region has an edge located in the first front end face, the second
region is contiguous with the first region and is located farther from
the first front end face than is the first region, the third region is a
region of the first surface other than the first and second regions, the
protruding portion lies on the first region, and has a first end face
constituting part of the first front end face, and a second end face
opposite to the first end face, the cladding includes a
receiving-portion-forming layer lying on the third region, the protruding
portion and the receiving-portion-forming layer define therebetween a
receiving portion, at least part of the first portion of the plasmon
generator is received in the receiving portion, the first portion of the
plasmon generator includes a first plasmon exciting portion opposed to
the second region, and a second plasmon exciting portion opposed to the
second end face of the protruding portion, the second region generates
first evanescent light based on the light propagating through the core,
the second end face of the protruding portion generates second evanescent
light based on the light propagating through the core, the plasmon
generator is configured so that a first surface plasmon is excited on the
first plasmon exciting portion through coupling with the first evanescent
light, and a second surface plasmon is excited on the second plasmon
exciting portion through coupling with the second evanescent light, and
the second front end face of the plasmon generator generates near-field
light based on the first and second surface plasmons.

2. The near-field light generator according to claim 1, wherein the
second end face of the protruding portion has a first edge in contact
with the first surface of the main body portion, and a second edge
farthest from the first surface, the second edge being located closer to
the first front end face of the core than is the first edge, and the
second plasmon exciting portion has a third edge in contact with the
first plasmon exciting portion, and a fourth edge in contact with the
second portion of the plasmon generator, the fourth edge being located
closer to the first front end face of the core than is the third edge.

3. The near-field light generator according to claim 1, wherein the
second portion of the plasmon generator includes a first metal layer, a
second metal layer, and an intermediate layer, the intermediate layer is
interposed between the first metal layer and the second metal layer, each
of the first metal layer, the second metal layer and the intermediate
layer has an end located in the second front end face, each of the first
and second metal layers is formed of a metal material, and the
intermediate layer is formed of a material that is higher in Vickers
hardness than the metal material used to form the first metal layer and
the metal material used to form the second metal layer.

4. A method of manufacturing the near-field light generator according to
claim 1, comprising the steps of: forming the core; forming the cladding;
and forming the plasmon generator after the step of forming the core.

5. The method of manufacturing the near-field light generator according
to claim 4, wherein the step of forming the core includes the step of
forming the main body portion and the step of forming the protruding
portion on the first region of the first surface of the main body
portion.

6. The method of manufacturing the near-field light generator according
to claim 5, wherein the second end face of the protruding portion has a
first edge in contact with the first surface of the main body portion,
and a second edge farthest from the first surface, the second edge being
located closer to the first front end face of the core than is the first
edge, and the second plasmon exciting portion has a third edge in contact
with the first plasmon exciting portion, and a fourth edge in contact
with the second portion of the plasmon generator, the fourth edge being
located closer to the first front end face of the core than is the third
edge.

7. The method of manufacturing the near-field light generator according
to claim 6, wherein the step of forming the protruding portion includes
the step of forming an initial protruding portion on the first region of
the first surface of the main body portion, and the step of taper-etching
the initial protruding portion so that the initial protruding portion is
provided with the second end face and thereby becomes the protruding
portion.

8. The method of manufacturing the near-field light generator according
to claim 4, wherein the step of forming the core includes the step of
forming an initial core having a top surface, and the step of partly
etching the top surface of the initial core so that the initial core
becomes the core.

9. The method of manufacturing the near-field light generator according
to claim 8, wherein the second end face of the protruding portion has a
first edge in contact with the first surface of the main body portion,
and a second edge farthest from the first surface, the second edge being
located closer to the first front end face of the core than is the first
edge, and the second plasmon exciting portion has a third edge in contact
with the first plasmon exciting portion, and a fourth edge in contact
with the second portion of the plasmon generator, the fourth edge being
located closer to the first front end face of the core than is the third
edge.

10. The method of manufacturing the near-field light generator according
to claim 4, wherein the step of forming the cladding includes the step of
forming the receiving-portion-forming layer before the step of forming
the plasmon generator.

11. The method of manufacturing the near-field light generator according
to claim 4, wherein the step of forming the plasmon generator includes
the step of forming the first portion and the step of forming the second
portion, and the step of forming the cladding includes the step of
forming the receiving-portion-forming layer that is performed
simultaneously with the step of forming the first portion.

12. A thermally-assisted magnetic recording head comprising: a medium
facing surface configured to face a recording medium; a main pole
configured to produce a write magnetic field for writing data on the
recording medium; and a near-field light generator, wherein the
near-field light generator includes: a waveguide including a core through
which light propagates, and a cladding provided around the core; and a
plasmon generator, the core has a first front end face lying at an end of
the core in a first direction, the first direction being a direction of
travel of the light propagating through the core, the plasmon generator
has a second front end face lying at an end of the plasmon generator in
the first direction, the second front end face being located in the
medium facing surface, the core and the plasmon generator are adjacent in
a second direction orthogonal to the first direction, the plasmon
generator includes a first portion and a second portion adjacent in the
second direction, the second portion including the second front end face,
the core includes a main body portion and a protruding portion adjacent
in the second direction, the main body portion has a first surface facing
toward the plasmon generator, and a second surface opposite to the first
surface, the first surface and the second surface being flat surfaces
parallel to each other, the first surface includes a first region, a
second region and a third region, the first region has an edge located in
the first front end face, the second region is contiguous with the first
region and is located farther from the first front end face than is the
first region, the third region is a region of the first surface other
than the first and second regions, the protruding portion lies on the
first region, and has a first end face constituting part of the first
front end face, and a second end face opposite to the first end face, the
cladding includes a receiving-portion-forming layer lying on the third
region, the protruding portion and the receiving-portion-forming layer
define therebetween a receiving portion, at least part of the first
portion of the plasmon generator is received in the receiving portion,
the first portion of the plasmon generator includes a first plasmon
exciting portion opposed to the second region, and a second plasmon
exciting portion opposed to the second end face of the protruding
portion, the second region generates first evanescent light based on the
light propagating through the core, the second end face of the protruding
portion generates second evanescent light based on the light propagating
through the core, the plasmon generator is configured so that a first
surface plasmon is excited on the first plasmon exciting portion through
coupling with the first evanescent light, and a second surface plasmon is
excited on the second plasmon exciting portion through coupling with the
second evanescent light, and the second front end face of the plasmon
generator generates near-field light based on the first and second
surface plasmons.

13. The thermally-assisted magnetic recording head according to claim 12,
wherein the second end face of the protruding portion has a first edge in
contact with the first surface of the main body portion, and a second
edge farthest from the first surface, the second edge being located
closer to the first front end face of the core than is the first edge,
and the second plasmon exciting portion has a third edge in contact with
the first plasmon exciting portion, and a fourth edge in contact with the
second portion of the plasmon generator, the fourth edge being located
closer to the first front end face of the core than is the third edge.

14. The thermally-assisted magnetic recording head according to claim 12,
wherein the second portion of the plasmon generator includes a first
metal layer, a second metal layer, and an intermediate layer, the
intermediate layer is interposed between the first metal layer and the
second metal layer, each of the first metal layer, the second metal layer
and the intermediate layer has an end located in the second front end
face, each of the first and second metal layers is formed of a metal
material, and the intermediate layer is formed of a material that is
higher in Vickers hardness than the metal material used to form the first
metal layer and the metal material used to form the second metal layer.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a near-field light generator for
use in thermally-assisted magnetic recording in which data is written on
a recording medium with its coercivity lowered by irradiating the
recording medium with near-field light, and to a thermally-assisted
magnetic recording head including the near-field light generator.

[0003] 2. Description of the Related Art

[0004] Recently, magnetic recording devices such as magnetic disk drives
have been improved in recording density, and thin-film magnetic heads and
recording media of improved performance have been demanded accordingly.
Among the thin-film magnetic heads, a composite thin-film magnetic head
has been used widely. The composite thin-film magnetic head has such a
structure that a read head unit including a magnetoresistive element
(hereinafter, also referred to as MR element) for reading and a write
head unit including an induction-type electromagnetic transducer for
writing are stacked on a substrate. In a magnetic disk drive, the
thin-film magnetic head is mounted on a slider configured to slightly fly
above the surface of a recording medium. The slider has a medium facing
surface to face the recording medium.

[0005] To increase the recording density of a magnetic recording device,
it is effective to make the magnetic fine particles of the recording
medium smaller. Making the magnetic fine particles smaller, however,
causes the problem that the magnetic fine particles drop in the thermal
stability of magnetization. To solve this problem, it is effective to
increase the anisotropic energy of the magnetic fine particles. However,
increasing the anisotropic energy of the magnetic fine particles leads to
an increase in coercivity of the recording medium, and this makes it
difficult to perform data writing with existing magnetic heads.

[0006] To solve the foregoing problems, there has been proposed a
technology so-called thermally-assisted magnetic recording. The
technology uses a recording medium having high coercivity. When writing
data, a write magnetic field and heat are simultaneously applied to the
area of the recording medium where to write data, whereby the area is
made to increase in temperature and drop in coercivity, and data is
written thereon. The area where data is written subsequently falls in
temperature and rises in coercivity to increase in thermal stability of
magnetization. Hereinafter, a magnetic head for use in thermally-assisted
magnetic recording will be referred to as a thermally-assisted magnetic
recording head.

[0007] In thermally-assisted magnetic recording, near-field light is
typically used as a means for applying heat to the recording medium. A
known method for generating near-field light is to use a plasmon
generator, which is a piece of metal that generates near-field light from
plasmons excited by irradiation with laser light. The laser light to be
used for generating near-field light is typically guided through a
waveguide, which is provided in the slider, to the plasmon generator
disposed near the medium facing surface of the slider. The waveguide
includes a core through which light propagates, and a cladding provided
around the core.

[0008] The plasmon generator has a front end face located in the medium
facing surface. The front end face generates near-field light. Surface
plasmons are excited on the plasmon generator and propagate along the
surface of the plasmon generator to reach the front end face. As a
result, the surface plasmons concentrate at the front end face, and
near-field light is generated from the front end face based on the
surface plasmons.

[0009] U.S. Patent Application Publication No. 2010/0172220 A1 discloses a
near-field light generator including a waveguide and a plasmon generator.
In the near-field light generator, the plasmon generator is disposed at a
predetermined distance from the core of the waveguide. In the near-field
light generator, evanescent light is generated at the surface of the core
and surface plasmons are excited on the surface of the plasmon generator
through coupling with the evanescent light.

[0010] Materials that are typically employed for plasmon generators are
metals having high electrical conductivities, such as Au and Ag. However,
Au and Ag are relatively soft and have relatively high thermal expansion
coefficients. Thus, forming an entire plasmon generator of Au or Ag gives
rise to problems as discussed below.

[0011] In the process of manufacturing a thermally-assisted magnetic
recording head, the medium facing surface is formed by polishing. During
polishing, polishing residues of metal materials may grow to cause
smears. To remove the smears, the polished surface is slightly etched by,
for example, ion beam etching in some cases. If an entire plasmon
generator is formed of Au or Ag, which is relatively soft, the polishing
and etching mentioned above may cause the front end face of the plasmon
generator to be significantly recessed relative to the other parts of the
medium facing surface. In such a case, the front end face of the plasmon
generator becomes distant from the recording medium, and the heating
performance of the plasmon generator is thus degraded.

[0012] Part of the energy of light propagating through the core is
transformed into heat in the plasmon generator. Part of the energy of
near-field light generated by the plasmon generator is also transformed
into heat in the plasmon generator. The plasmon generator thus rises in
temperature during the operation of the thermally-assisted magnetic
recording head. If the entire plasmon generator is formed of Au or Ag,
the rise in temperature of the plasmon generator causes the plasmon
generator to expand and significantly protrude toward the recording
medium. This in turn may cause a protective film covering the medium
facing surface to come into contact with the recording medium and thereby
damage the recording medium or be broken. When the protective film is
broken, the plasmon generator may be damaged by contact with the
recording medium or may be corroded by contact with high temperature air.

[0013] Further, if the entire plasmon generator is formed of Au or Ag, the
temperature rise of the plasmon generator may result in deformation of
the plasmon generator due to aggregation. In addition, such a plasmon
generator expands when its temperature rises and then contracts when its
temperature drops. When the plasmon generator undergoes such a process,
the front end face of the plasmon generator may be significantly recessed
relative to the other parts of the medium facing surface. In such a case,
the heating performance of the plasmon generator is degraded as mentioned
above.

[0014] For the various reasons described above, a plasmon generator that
is formed entirely of Au or Ag has the drawback of being low in
reliability. The drawback becomes more noticeable if the front end face
of the plasmon generator is large in area.

[0015] U.S. Patent Application Publication No. 2010/0172220 A1 discloses a
plasmon generator shaped such that the thickness of a portion of the
plasmon generator near the front end face decreases toward the front end
face. This plasmon generator allows for a reduction in the area of the
front end face. U.S. Patent Application Publication No. 2010/0172220 A1
further discloses a structure in which the plasmon generator has a
propagation edge or a propagation surface to allow surface plasmons to
propagate therethrough, and a groove for receiving at least a portion of
the propagation edge or the propagation surface is formed in a top
surface of the core having the top surface and a bottom surface. This
structure aims at exciting a lot of surface plasmons on the propagation
edge or the propagation surface.

[0016] The above-described structure, however, has a drawback that the
efficiency of excitation of surface plasmons on the plasmon generator
suffers a reduction due to the groove. This will now be described in
detail. To begin with, we will consider a first cross section which
passes through an edge of the groove closest to the light-incidence end
of the core and is perpendicular to the direction of travel of the light
propagating through the core. Then, a portion of the core that is located
closer to the light-incidence end relative to the first cross section
will be referred to as the first portion, and another portion of the core
that is located farther from the light-incidence end relative to the
first cross section will be referred to as the second portion.

[0017] Next, we will consider a second cross section which is parallel to
the direction of travel of the light propagating through the core and
perpendicular to the bottom surface of the core. On the second cross
section, the dimension of the core in a direction perpendicular to the
bottom surface of the core is defined as thickness. The first portion
does not include the groove, whereas the second portion includes the
groove. Consequently, the second portion is smaller in thickness than the
first portion. Further, the center of the second portion in the thickness
direction does not coincide with the center of the first portion in the
thickness direction.

[0018] Next, we will consider a typical core having no groove and having a
constant thickness. When such a typical core is used to excite surface
plasmons on the plasmon generator, the greatest efficiency of propagation
of light through the core and the greatest efficiency of excitation of
surface plasmons on the plasmon generator are achieved when the optical
axis of the light incident on the core coincides with the center of the
core in the thickness direction.

[0019] To allow light to enter the first portion of the core having the
groove, the optical axis of the light is typically aligned with the
center of the first portion in the thickness direction. This is for the
purpose of achieving the greatest efficiency of propagation of the light
through the first portion. The light having entered the first portion
propagates through the first portion and enters the second portion. As
mentioned above, the center of the second portion in the thickness
direction does not coincide with the center of the first portion in the
thickness direction. Consequently, when the light enters the second
portion, its optical axis does not coincide with the center of the second
portion in the thickness direction. This results in a reduced efficiency
of propagation of the light through the second portion. As a result, the
efficiency of excitation of surface plasmons on the plasmon generator is
also reduced.

Object and Summary of the Invention

[0020] It is an object of the present invention to provide a near-field
light generator including a waveguide and a plasmon generator, the
near-field light generator allowing a lot of surface plasmons to be
excited on the plasmon generator and allowing the plasmon generator to
operate with high reliability, and to provide a thermally-assisted
magnetic recording head including such a near-field light generator.

[0021] A thermally-assisted magnetic recording head of the present
invention includes a medium facing surface configured to face a recording
medium, a main pole configured to produce a write magnetic field for
writing data on the recording medium, and a near-field light generator of
the present invention. The near-field light generator of the present
invention includes a waveguide and a plasmon generator. The waveguide
includes a core through which light propagates, and a cladding provided
around the core.

[0022] The core has a first front end face lying at an end of the core in
a first direction, the first direction being the direction of travel of
the light propagating through the core. The plasmon generator has a
second front end face lying at an end of the plasmon generator in the
first direction. In the thermally-assisted magnetic recording head of the
present invention, the second front end face is located in the medium
facing surface.

[0023] The core and the plasmon generator are adjacent in a second
direction orthogonal to the first direction. The plasmon generator
includes a first portion and a second portion adjacent in the second
direction. The second portion includes the second front end face.

[0024] The core includes a main body portion and a protruding portion
adjacent in the second direction. The main body portion has a first
surface facing toward the plasmon generator, and a second surface
opposite to the first surface. The first and second surfaces are flat
surfaces parallel to each other. The first surface includes a first
region, a second region and a third region. The first region has an edge
located in the first front end face. The second region is contiguous with
the first region and is located farther from the first front end face
than is the first region. The third region is a region of the first
surface other than the first and second regions.

[0025] The protruding portion lies on the first region, and has a first
end face constituting part of the first front end face, and a second end
face opposite to the first end face. The cladding includes a
receiving-portion-forming layer lying on the third region. The protruding
portion and the receiving-portion-forming layer define therebetween a
receiving portion. At least part of the first portion of the plasmon
generator is received in the receiving portion.

[0026] The first portion of the plasmon generator includes a first plasmon
exciting portion opposed to the second region, and a second plasmon
exciting portion opposed to the second end face of the protruding
portion. The second region generates first evanescent light based on the
light propagating through the core. The second end face of the protruding
portion generates second evanescent light based on the light propagating
through the core.

[0027] In the near-field light generator and the thermally-assisted
magnetic recording head of the present invention, the plasmon generator
is configured so that a first surface plasmon is excited on the first
plasmon exciting portion through coupling with the first evanescent
light, and a second surface plasmon is excited on the second plasmon
exciting portion through coupling with the second evanescent light. The
second front end face of the plasmon generator generates near-field light
based on the first and second surface plasmons.

[0028] In the near-field light generator and the thermally-assisted
magnetic recording head of the present invention, the second end face of
the protruding portion may have a first edge in contact with the first
surface of the main body portion, and a second edge farthest from the
first surface. The second edge may be located closer to the first front
end face of the core than is the first edge. The second plasmon exciting
portion may have a third edge in contact with the first plasmon exciting
portion, and a fourth edge in contact with the second portion of the
plasmon generator. The fourth edge may be located closer to the first
front end face of the core than is the third edge.

[0029] In the near-field light generator and the thermally-assisted
magnetic recording head of the present invention, the second portion of
the plasmon generator may include a first metal layer, a second metal
layer, and an intermediate layer. The intermediate layer is interposed
between the first metal layer and the second metal layer. Each of the
first metal layer, the second metal layer and the intermediate layer has
an end located in the second front end face. Each of the first and second
metal layers is formed of a metal material. The intermediate layer is
formed of a material that is higher in Vickers hardness than the metal
material used to form the first metal layer and the metal material used
to form the second metal layer.

[0030] A method of manufacturing the near-field light generator of the
present invention includes the steps of forming the core; forming the
cladding; and forming the plasmon generator after the step of forming the
core.

[0031] In the method of manufacturing the near-field light generator of
the present invention, the step of forming the core may include the step
of forming the main body portion and the step of forming the protruding
portion on the first region of the first surface of the main body
portion. In this case, the second end face of the protruding portion has
a first edge in contact with the first surface of the main body portion,
and a second edge farthest from the first surface. The second edge may be
located closer to the first front end face of the core than is the first
edge. The second plasmon exciting portion may have a third edge in
contact with the first plasmon exciting portion, and a fourth edge in
contact with the second portion of the plasmon generator. The fourth edge
may be located closer to the first front end face of the core than is the
third edge. The step of forming the protruding portion may include the
step of forming an initial protruding portion on the first region of the
first surface of the main body portion, and the step of taper-etching the
initial protruding portion so that the initial protruding portion is
provided with the second end face and thereby becomes the protruding
portion.

[0032] In the method of manufacturing the near-field light generator of
the present invention, the step of forming the core may include the step
of forming an initial core having a top surface, and the step of partly
etching the top surface of the initial core so that the initial core
becomes the core. In this case, the second end face of the protruding
portion has a first edge in contact with the first surface of the main
body portion, and a second edge farthest from the first surface. The
second edge may be located closer to the first front end face of the core
than is the first edge. The second plasmon exciting portion may have a
third edge in contact with the first plasmon exciting portion, and a
fourth edge in contact with the second portion of the plasmon generator.
The fourth edge may be located closer to the first front end face of the
core than is the third edge.

[0033] In the method of manufacturing the near-field light generator of
the present invention, the step of forming the cladding may include the
step of forming the receiving-portion-forming layer before the step of
forming the plasmon generator. Alternatively, the step of forming the
plasmon generator may include the step of forming the first portion and
the step of forming the second portion. The step of forming the cladding
may include the step of forming the receiving-portion-forming layer that
is performed simultaneously with the step of forming the first portion.

[0034] In the present invention, the plasmon generator includes the first
portion and the second portion. The second portion includes the second
front end face. The first portion includes the first plasmon exciting
portion and the second plasmon exciting portion. These features make it
possible to reduce the area of the second front end face and thereby
enhance the reliability of the plasmon generator.

[0035] Further, in the present invention, the first and second surfaces of
the main body portion of the core are flat surfaces parallel to each
other, and the first surface includes the second region to generate the
first evanescent light. Consequently, in the course of travel of the
light propagating through the main body portion of the core to reach the
second region, there is no reduction in efficiency of propagation of the
light. This makes it possible to excite a lot of first surface plasmons
on the first plasmon exciting portion.

[0036] Further, the present invention allows the second evanescent light
to be generated from the second end face of the protruding portion of the
core, and thereby allows the second surface plasmon to be excited on the
second plasmon exciting portion of the plasmon generator.

[0037] Consequently, the present invention makes it possible to provide a
near-field light generator that allows a lot of surface plasmons to be
excited on a plasmon generator and allows the plasmon generator to
operate with high reliability, and to provide a thermally-assisted
magnetic recording head including such a near-field light generator.

[0038] Other and further objects, features and advantages of the present
invention will appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a cross-sectional view showing the main part of a
thermally-assisted magnetic recording head according to a first
embodiment of the invention.

[0040] FIG. 2 is a perspective view of the core of the waveguide shown in
FIG. 1.

[0041] FIG. 3 is a perspective view of the plasmon generator shown in FIG.
1.

[0042] FIG. 4 is a plan view showing the positional relationship between
the plasmon generator and the core of the waveguide shown in FIG. 1.

[0043] FIG. 5 is a cross-sectional view showing the configuration of the
thermally-assisted magnetic recording head according to the first
embodiment of the invention.

[0044] FIG. 6 is a front view showing the medium facing surface of the
thermally-assisted magnetic recording head according to the first
embodiment of the invention.

[0045] FIG. 7 is a cross-sectional view showing a step of a method of
manufacturing the thermally-assisted magnetic recording head according to
the first embodiment of the invention.

[0046] FIG. 8 is a cross-sectional view showing a step that follows the
step shown in FIG. 7.

[0047] FIG. 9 is a cross-sectional view showing a step that follows the
step shown in FIG. 8.

[0048] FIG. 10 is a cross-sectional view showing a step that follows the
step shown in FIG. 9.

[0049] FIG. 11 is a cross-sectional view showing a step that follows the
step shown in FIG. 10.

[0050] FIG. 12 is a cross-sectional view showing a step that follows the
step shown in FIG. 11.

[0051] FIG. 13 is a cross-sectional view showing a step that follows the
step shown in FIG. 12.

[0052] FIG. 14 is a cross-sectional view showing a step that follows the
step shown in FIG. 13.

[0053] FIG. 15 is a plan view showing a step that follows the step shown
in FIG. 14.

[0054] FIG. 16 is a cross-sectional view showing a cross section taken
along line 16-16 in FIG. 15.

[0055] FIG. 17 is a cross-sectional view showing a step of a method of
manufacturing a thermally-assisted magnetic recording head according to a
second embodiment of the invention.

[0056] FIG. 18 is a cross-sectional view showing a step that follows the
step shown in FIG. 17.

[0057] FIG. 19 is a cross-sectional view showing the main part of a
thermally-assisted magnetic recording head according to a third
embodiment of the invention.

[0058] FIG. 20 is a cross-sectional view showing a step of a method of
manufacturing the thermally-assisted magnetic recording head according to
the third embodiment of the invention.

[0059] FIG. 21 is a cross-sectional view showing a step that follows the
step shown in FIG. 20.

[0060] FIG. 22 is a cross-sectional view showing the main part of a
thermally-assisted magnetic recording head according to a fourth
embodiment of the invention.

[0061] FIG. 23 is a cross-sectional view showing a step of a method of
manufacturing the thermally-assisted magnetic recording head according to
the fourth embodiment of the invention.

[0062] FIG. 24 is a cross-sectional view showing a step that follows the
step shown in FIG. 23.

[0063] FIG. 25 is a cross-sectional view showing a step that follows the
step shown in FIG. 24.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

[0064] Preferred embodiments of the present invention will now be
described in detail with reference to the drawings. First, reference is
made to FIG. 5 and FIG. 6 to describe the configuration of a
thermally-assisted magnetic recording head according to a first
embodiment of the invention. FIG. 5 is a cross-sectional view showing the
configuration of the thermally-assisted magnetic recording head. FIG. 6
is a front view showing the medium facing surface of the
thermally-assisted magnetic recording head.

[0065] The thermally-assisted magnetic recording head according to the
present embodiment is intended for perpendicular magnetic recording, and
is in the form of a slider to fly over the surface of a rotating
recording medium. When the recording medium rotates, an airflow passing
between the recording medium and the slider causes a lift to be exerted
on the slider. The slider is configured to fly over the surface of the
recording medium by means of the lift.

[0066] As shown in FIG. 5, the thermally-assisted magnetic recording head
has a medium facing surface 60 configured to face a recording medium 80.
Here, X direction, Y direction, and Z direction will be defined as
follows. The X direction is the direction across the tracks of the
recording medium 80, i.e., the track width direction. The Y direction is
a direction perpendicular to the medium facing surface 60. The Z
direction is the direction of travel of the recording medium 80 as viewed
from the slider. The X, Y, and Z directions are orthogonal to one
another.

[0067] As shown in FIG. 5 and FIG. 6, the thermally-assisted magnetic
recording head includes: a substrate 1 formed of a ceramic material such
as aluminum oxide-titanium carbide (Al2O3--TiC) and having a
top surface 1a; an insulating layer 2 formed of an insulating material
such as alumina (Al2O3) and disposed on the top surface 1a of
the substrate 1; a bottom shield layer 3 formed of a magnetic material
and disposed on the insulating layer 2; a bottom shield gap film 4 which
is an insulating film disposed to cover the bottom shield layer 3; a
magnetoresistive (MR) element 5 serving as a read element disposed on the
bottom shield gap film 4; two leads (not illustrated) connected to the MR
element 5; a top shield gap film 6 which is an insulating film disposed
on the MR element 5; and a top shield layer 7 formed of a magnetic
material and disposed on the top shield gap film 6. The Z direction is
also a direction perpendicular to the top surface 1a of the substrate 1.

[0068] An end of the MR element 5 is located in the medium facing surface
60. The MR element 5 may be an element formed of a magneto-sensitive film
that exhibits a magnetoresistive effect, such as an anisotropic
magnetoresistive (AMR) element, a giant magnetoresistive (GMR) element,
or a tunneling magnetoresistive (TMR) element. The GMR element may be of
either the current-in-plane (CIP) type in which a current used for
detecting magnetic signals is fed in a direction generally parallel to
the plane of layers constituting the GMR element or the
current-perpendicular-to-plane (CPP) type in which the current used for
detecting magnetic signals is fed in a direction generally perpendicular
to the plane of layers constituting the GMR element.

[0069] The parts from the bottom shield layer 3 to the top shield layer 7
constitute a read head unit. The thermally-assisted magnetic recording
head further includes: an insulating layer 8 disposed on the top shield
layer 7; a middle shield layer 9 formed of a magnetic material and
disposed on the insulating layer 8; and a nonmagnetic layer 10 formed of
a nonmagnetic material and disposed on the middle shield layer 9. The
insulating layer 8 and the nonmagnetic layer 10 are formed of alumina,
for example.

[0070] The thermally-assisted magnetic recording head further includes a
return pole layer 11 formed of a magnetic material and disposed on the
nonmagnetic layer 10, and an insulating layer (not illustrated) disposed
on the nonmagnetic layer 10 and surrounding the return pole layer 11. The
return pole layer 11 has an end face located in the medium facing surface
60. The non-illustrated insulating layer is formed of alumina, for
example.

[0071] The thermally-assisted magnetic recording head further includes: a
shield layer 12 located near the medium facing surface 60 and lying on a
portion of the return pole layer 11; a coupling layer 13 located away
from the medium facing surface 60 and lying on another portion of the
return pole layer 11; an insulating layer 14 lying on the remaining
portion of the return pole layer 11 and on the non-illustrated insulating
layer; and a coil 15 lying on the insulating layer 14. The shield layer
12 and the coupling layer 13 are each formed of a magnetic material. The
shield layer 12 has an end face located in the medium facing surface 60.
The coil 15 is planar spiral-shaped and wound around the coupling layer
13. The coil 15 is formed of a conductive material such as copper. The
insulating layer 14 is formed of alumina, for example.

[0072] The thermally-assisted magnetic recording head further includes an
insulating layer 16 disposed around the shield layer 12, the coupling
layer 13 and the coil 15 and in the space between every adjacent turns of
the coil 15, and two coupling portions 17A and 17B disposed on the
coupling layer 13. The coupling portions 17A and 17B are each formed of a
magnetic material. Each of the coupling portions 17A and 17B includes a
first layer located on the coupling layer 13, and a second and a third
layer stacked in this order on the first layer. The first layer of the
coupling portion 17A and the first layer of the coupling portion 17B are
aligned in the track width direction (the X direction). The insulating
layer 16 is formed of alumina, for example.

[0073] The thermally-assisted magnetic recording head further includes a
waveguide, the waveguide including a core 20 through which light
propagates, and a cladding provided around the core 20. The core 20 will
be described in detail later.

[0074] The cladding includes cladding layers 18, 19 and 24, and a
receiving-portion-forming layer 23. The cladding layer 18 lies on the
shield layer 12, the coupling layer 13, the coil 15 and the insulating
layer 16. The core 20 lies on the cladding layer 18. The cladding layer
19 lies on the cladding layer 18 and surrounds the core 20. The
receiving-portion-forming layer 23 lies on the cladding layer 19 and a
portion of the core 20. The cladding layer 24 lies on another portion of
the core 20 and the receiving-portion-forming layer 23.

[0075] The core 20 is formed of a dielectric material that transmits laser
light to be used for generating near-field light. The laser light emitted
from a laser diode (not illustrated) enters the core 20 and propagates
through the core 20. The cladding layers 18, 19 and 24 and the
receiving-portion-forming layer 23 are each formed of a dielectric
material that has a refractive index lower than that of the core 20. For
example, the core 20 may be formed of tantalum oxide such as
Ta2O5 or silicon oxynitride (SiON), while the cladding layers
18, 19 and 24 and the receiving-portion-forming layer 23 may be formed of
silicon dioxide (SiO2) or alumina.

[0076] The first layers of the coupling portions 17A and 17B are embedded
in the cladding layer 18. The second layers of the coupling portions 17A
and 17B are embedded in the cladding layer 19. The second layer of the
coupling portion 17A and the second layer of the coupling portion 17B are
located on opposite sides of the core 20 in the track width direction
(the X direction), and are each at a distance from the core 20.

[0077] The thermally-assisted magnetic recording head further includes: a
main pole 29 located near the medium facing surface 60 and lying above
the core 20; a plasmon generator 40 located between the core 20 and the
main pole 29; and an adhesion layer 39 interposed between the cladding
layer 24 and the plasmon generator 40. The plasmon generator 40 is
configured to excite surface plasmons on the principle to be described
later. The adhesion layer 39 is to prevent the plasmon generator 40 from
peeling away from the cladding layer 24. The adhesion layer 39 may be
formed of one of Zr, ZrN, Ru, Pt, Pd, Ti, Ta, Ni, W, Cr, NiCr, NiFe, Co,
Cu, TiW, TiN, Mo, Hf, and Rh, for example. The adhesion layer 39 may have
a thickness of 0.3 to 1 nm, for example. The adhesion layer 39 is not an
essential component of the thermally-assisted magnetic recording head,
and can be dispensed with. The plasmon generator 40 will be described in
detail later.

[0078] The main pole 29 has an end face 29a located in the medium facing
surface 60. The main pole 29 may include a narrow portion having the end
face 29a and an end opposite to the end face 29a, and a wide portion
connected to the end of the narrow portion. The wide portion is greater
than the narrow portion in width in the track width direction (the X
direction).

[0079] The thermally-assisted magnetic recording head further includes: a
dielectric layer 25 lying on the cladding layer 24 and surrounding the
plasmon generator 40; a heat sink 26 lying astride part of the plasmon
generator 40 and part of the dielectric layer 25; a dielectric layer 27
disposed to cover the heat sink 26; and a dielectric layer 28 disposed to
cover the plasmon generator 40 and the dielectric layer 27. The heat sink
26 has a maximum thickness in the range of 200 to 500 nm, for example.
The dielectric layer 27 has a top surface, and an end face closest to the
medium facing surface 60. The distance from the medium facing surface 60
to an arbitrary point on the aforementioned end face of the dielectric
layer 27 decreases with decreasing distance from the arbitrary point to
the top surface 1a of the substrate 1. The dielectric layer 27 has a
maximum thickness in the range of 200 to 800 nm, for example.

[0080] The main pole 29 is disposed on the dielectric layer 28 so as to
lie above part of each of the top surface of the plasmon generator 40,
the end face of the dielectric layer 27 and the top surface of the
dielectric layer 27. The dielectric layer 28 has a thickness in the range
of, for example, 10 to 40 nm, preferably in the range of 15 to 25 nm.

[0081] The third layers of the coupling portions 17A and 17B are embedded
in the receiving-portion-forming layer 23, the cladding layer 24 and the
dielectric layers 25, 27 and 28. The dielectric layers 25, 27 and 28 may
be formed of SiO2 or alumina, for example. The heat sink 26 is
formed of a material having a high thermal conductivity, such as Au, Ag,
Al, or Cu. The heat sink 26 has the function of dissipating heat
generated at the plasmon generator 40. The heat sink 26 is not an
essential component of the thermally-assisted magnetic recording head,
and can be dispensed with.

[0082] The thermally-assisted magnetic recording head further includes a
coupling layer 30 formed of a magnetic material and disposed over the
third layers of the coupling portions 17A and 17B and the dielectric
layer 28, and a dielectric layer 31 disposed around the main pole 29 and
the coupling layer 30. The top surfaces of the main pole 29, the coupling
layer 30 and the dielectric layer 31 are even with each other. The
dielectric layer 31 is formed of SiO2 or alumina, for example.

[0083] The thermally-assisted magnetic recording head further includes a
coil 32 disposed on the dielectric layer 31, an insulating layer 33
disposed to cover the coil 32, and a yoke layer 34 formed of a magnetic
material and disposed over the main pole 29, the coupling layer 30 and
the insulating layer 33. The yoke layer 34 magnetically couples the main
pole 29 and the coupling layer 30 to each other. The coil 32 is planar
spiral-shaped and wound around a portion of the yoke layer 34 that lies
on the coupling layer 30. The coil 32 is formed of a conductive material
such as copper. The insulating layer 33 is formed of alumina, for
example.

[0084] The thermally-assisted magnetic recording head further includes a
protective layer 35 disposed to cover the yoke layer 34. The protective
layer 35 is formed of alumina, for example.

[0085] The parts from the return pole layer 11 to the yoke layer 34
constitute a write head unit. The coils 15 and 32 produce magnetic fields
corresponding to data to be written on the recording medium 80. The
shield layer 12, the return pole layer 11, the coupling layer 13, the
coupling portions 17A and 17B, the coupling layer 30, the yoke layer 34,
and the main pole 29 form a magnetic path for passing magnetic fluxes
corresponding to the magnetic fields produced by the coils 15 and 32. The
coils 15 and 32 are connected in series or in parallel so that the
magnetic flux corresponding to the magnetic field produced by the coil 15
and the magnetic flux corresponding to the magnetic field produced by the
coil 32 flow in the same direction through the main pole 29. The main
pole 29 allows the magnetic flux corresponding to the magnetic field
produced by the coil 15 and the magnetic flux corresponding to the
magnetic field produced by the coil 32 to pass, and produces a write
magnetic field for writing data on the recording medium 80 by means of a
perpendicular magnetic recording system.

[0086] The coil 15 is not an essential component of the thermally-assisted
magnetic recording head, and can be dispensed with. The coil 32 may be
wound helically around the yoke layer 34.

[0087] As has been described, the thermally-assisted magnetic recording
head according to the present embodiment includes the medium facing
surface 60, the read head unit, and the write head unit. The read head
unit and the write head unit are stacked on the substrate 1. The write
head unit is located on the trailing side, i.e., the front side in the
direction of travel of the recording medium 80 (the Z direction) relative
to the read head unit.

[0088] The thermally-assisted magnetic recording head may include a
protective film covering the medium facing surface 60. The protective
film may be formed of diamond-like-carbon (DLC) or Ta2O5, for
example. The protective film is not an essential component of the
thermally-assisted magnetic recording head and can be dispensed with.

[0089] The write head unit includes the coils 15 and 32, the main pole 29,
and a near-field light generator according to the present embodiment. The
near-filed light generator includes the waveguide and the plasmon
generator 40. The waveguide includes the core 20 and the cladding. The
cladding includes the cladding layers 18, 19 and 24 and the
receiving-portion-forming layer 23. The main pole 29 is located on the
front side in the direction of travel of the recording medium 80 (the Z
direction) relative to the core 20. The plasmon generator 40 is located
between the core 20 and the main pole 29.

[0090] The core 20 and the plasmon generator 40 will now be described in
detail with reference to FIG. 1 to FIG. 5. FIG. 1 is a cross-sectional
view showing the main part of the thermally-assisted magnetic recording
head according to the present embodiment. FIG. 2 is a perspective view of
the core 20 shown in FIG. 1. FIG. 3 is a perspective view of the plasmon
generator 40 shown in FIG. 1. FIG. 4 is a plan view showing the
positional relationship between the plasmon generator 40 and the core 20
of the waveguide shown in FIG. 1.

[0091] As shown in FIG. 5, the core 20 extends in a direction
perpendicular to the medium facing surface 60 (the Y direction). In FIG.
5, the arrow labeled 50 indicates the direction of travel of laser light
50 propagating through the core 20. The direction of travel of the laser
light 50 is parallel to the Y direction and toward the medium facing
surface 60. The direction of travel of the laser light 50 (the Y
direction) corresponds to the "first direction" in the present invention.
As shown in FIG. 1, FIG. 2 and FIG. 4, the core 20 has a first front end
face 20a lying at an end of the core 20 in the direction of travel of the
laser light 50 (the first direction). In the present embodiment, the
first front end face 20a is located in the medium facing surface 60.

[0092] The Z direction corresponds to the "second direction" in the
present invention, and is orthogonal to the direction of travel of the
laser light 50 (the first direction). The core 20 and the plasmon
generator 40 are adjacent in the Z direction (the second direction). In
the present embodiment, the plasmon generator 40 is located on the front
side in the Z direction (the second direction) relative to the core 20.

[0093] The core 20 includes a main body portion 21 and a protruding
portion 22 adjacent in the Z direction (the second direction). As shown
in FIG. 1, FIG. 2 and FIG. 4, the main body portion 21 has: an end face
21a constituting part of the first front end face 20a; a first surface
21b which is a top surface facing toward the plasmon generator 40; a
second surface 21c opposite to the first surface 21b; two side surfaces
21d and 21e; and an incidence end (not illustrated). The first and second
surfaces 21b and 21c are flat surfaces parallel to each other. Both of
the first and second surfaces 21b and 21c are perpendicular to the Z
direction (the second direction), or equivalently, parallel to the XY
plane.

[0094] As shown in FIG. 1 and FIG. 2, the first surface 21b includes a
first region R1, a second region R2 and a third region R3. The first
region R1 is the region on which the protruding portion 22 lies. The
first region R1 has an edge located in the first front end face 20a. The
second region R2 is the region opposed to part of the plasmon generator
40. The second region R2 is contiguous with the first region R1 and is
located farther from the first front end face 20a than is the first
region R1. The width of the second region R2 in the X direction decreases
toward the first region R1. The third region R3 is a region of the first
surface 21b other than the first and second regions R1 and R2.

[0095] As shown in FIG. 1, FIG. 2 and FIG. 4, the protruding portion 22
lies on the first region R1. The protruding portion 22 is shaped to be
long in the X direction. The protruding portion 22 has: a first end face
22a constituting part of the first front end face 20a; a second end face
22b opposite to the first end face 22a; a top surface 22c; a bottom
surface 22d; and two side surfaces 22e and 22f. The two side surfaces 22e
and 22f are located more inwardly in the X direction than the two side
surfaces 21d and 21e of the main body portion 21.

[0096] In the present embodiment, the second end face 22b is inclined with
respect to the medium facing surface 60. More specifically, as shown in
FIG. 1 and FIG. 2, the second end face 22b has a first edge E1 in contact
with the first surface 21b of the main body portion 21, and a second edge
E2 farthest from the first surface 21b. The second edge E2 is located
closer to the first front end face 20a of the core 20 than is the first
edge E1. The distance from the medium facing surface 60 to an arbitrary
point on the second end face 22b decreases with increasing distance from
the arbitrary point to the first edge E1. The second end face 22b
preferably forms an angle in the range of, for example, 45° to
80° with respect to the Z direction (the second direction).

[0097] As shown in FIG. 1 and FIG. 2, the receiving-portion-forming layer
23 lies on the third region R3 and has a top surface 23a. The top surface
23a of the receiving-portion-forming layer 23 is located at the same
level as the top surface 22c of the protruding portion 22. Portions of
the receiving-portion-forming layer 23 located on opposite sides of the
second region R2 in the X direction are in contact with the second end
face 22b of the protruding portion 22. The protruding portion 22 and the
receiving-portion-forming layer 23 define therebetween a receiving
portion 200. The receiving portion 200 is located near the first front
end face 20a, and the planar shape, i.e., the shape as viewed from above,
of the receiving portion 200 corresponds to that of a first portion of
the plasmon generator 40 to be described later. As shown in FIG. 2, the
receiving-portion-forming layer 23 has five wall faces defining the
periphery of the receiving portion 200. The cladding layer 24 covers the
second region R2 of the first surface 21b, part of the second end face
22b of the protruding portion 22, the five wall faces of the
receiving-portion-forming layer 23, the top surface 22c of the protruding
portion 22, and the top surface 23a of the receiving-portion-forming
layer 23.

[0098] In FIG. 1 and FIG. 2, the symbol 23b represents one of the five
wall faces of the receiving-portion-forming layer 23 that is located
farther from the medium facing surface 60 than is the second region R2.
This wall face 23b may be perpendicular to the Y direction, or
equivalently, parallel to the medium facing surface 60, or may be
inclined with respect to the medium facing surface 60. Where the wall
face 23b is inclined with respect to the medium facing surface 60, the
distance from the medium facing surface 60 to an arbitrary point on the
wall face 23b increases with increasing distance from the arbitrary point
to the first surface 21b of the main body portion 21. FIG. 1 and FIG. 2
show an example in which the wall face 23b is inclined with respect to
the medium facing surface 60.

[0099] As shown in FIG. 1, FIG. 3 and FIG. 4, the plasmon generator 40 has
a second front end face 40a lying at an end of the plasmon generator 40
in the direction of travel of the laser light 50 (the first direction),
and a rear end face 40b opposite to the second front end face 40a. The
second front end face 40a generates near-field light on the principle to
be described later. The second front end face 40a is located in the
medium facing surface 60 along with the first front end face 20a of the
core 20 and the end face 29a of the main pole 29.

[0100] As shown in FIG. 1, the plasmon generator 40 includes a first metal
portion 401, a multilayer film portion 402, and a second metal portion
403. The first metal portion 401 lies on the adhesion layer 39. The first
metal portion 401 has a top surface located at a higher level than the
top surface of a portion of the adhesion layer 39 that lies on the top
surface 22c of the protruding portion 22 and the top surface 23a of the
receiving-portion-forming layer 23. The multilayer film portion 402 and
the second metal portion 403 lie on the first metal portion 401. The heat
sink 26 is in contact with the top surfaces of the multilayer film
portion 402 and the second metal portion 403.

[0101] The first metal portion 401 is formed of a metal material. The
metal material used to form the first metal portion 401 may be one of Au,
Ag, Al and Cu, for example.

[0102] As shown in FIG. 1, the first metal portion 401 includes a main
portion 401A and a bonding portion 401B. In FIG. 1 the boundary between
the main portion 401A and the bonding portion 401B is indicated in a
dotted line. Most part of the main portion 401A is received in the
receiving portion 200 with the cladding layer 24 and the adhesion layer
39 interposed between the main portion 401A and each of the main body
portion 21, the protruding portion 22 and the receiving-portion-forming
layer 23. The boundary between the main portion 401A and the bonding
portion 401B is located at the same level as the top surface of the
portion of the adhesion layer 39 that lies on the top surface 22c of the
protruding portion 22 and the top surface 23a of the
receiving-portion-forming layer 23. The bonding portion 401B has an end
located in the second front end face 40a and an end located in the rear
end face 40b, and lies astride the main portion 401A and the adhesion
layer 39. The bonding portion 401B has the function of bonding the
multilayer film portion 402 and the second metal portion 403 to the main
portion 401A.

[0103] The main portion 401A has a thickness in the range of 80 to 300 nm,
for example. The bonding portion 401B has a thickness in the range of 1
to 5 nm, for example.

[0104] As shown in FIG. 3, the multilayer film portion 402 includes at
least a first metal layer M1, a second metal layer M2, and an
intermediate layer N1. The intermediate layer N1 is interposed between
the first metal layer M1 and the second metal layer M2. Each of the first
metal layer M1, the second metal layer M2 and the intermediate layer N1
has an end located in the second front end face 40a. Each of the first
and second metal layers M1 and M2 is formed of a metal material. The
intermediate layer N1 is formed of a material that is higher in Vickers
hardness than the metal material used to form the first metal layer M1
and the metal material used to form the second metal layer M2. The
material used to form the intermediate layer N1 may be a metal material
different from the metal material used to form the first metal layer M1
and the metal material used to form the second metal layer M2, or may be
a dielectric material. Hereinafter, the metal material used to form the
first metal layer M1 and the metal material used to form the second metal
layer M2 will each be referred to as the metal layer material, and the
material used to form the intermedite layer N1 will be referred to as the
intermediate layer material. The intermediate layer material is higher in
Vickers hardness than the metal layer material. Where the intermediate
layer material is a metal material, the metal layer material is
preferably higher in electrical conductivity than the intermediate layer
material.

[0105] In the example shown in FIG. 1, the intermediate layer N1 and the
second metal layer M2 are stacked in this order on the first metal layer
M1. In this example, the multilayer film portion 402 further includes a
second intermediate layer N2, a third metal layer M3, a third
intermediate layer N3, a fourth metal layer M4, and a protective layer N4
stacked in this order on the second metal layer M2. Each of the second
intermediate layer N2, the third metal layer M3, the third intermediate
layer N3, the fourth metal layer M4 and the protective layer N4 has an
end located in the second front end face 40a. Each of the metal layers M3
and M4 is formed of the metal layer material. Each of the intermediate
layers N2 and N3 and the protective layer N4 is formed the intermediate
layer material. The protective layer N4 has the function of protecting
the plasmon generator 40 and the function of enhancing adhesion of the
dielectric layers 27 and 28 to the plasmon generator 40.

[0107] As far as the requirement that the intermediate layer material be
higher in Vickers hardness than the metal layer material is satisfied,
the materials used to form the metal layers M1 to M4 may all be the same
or may be different from each other, or some of them may be the same.
Likewise, the materials used to form the intermediate layers N1 to N3 and
the protective layer N4 may all be the same or may be different from each
other, or some of them may be the same.

[0108] The intermediate layers N1 to N3 and the protective layer N4 may be
smaller in thickness than the metal layers M1 to M4. The thickness of
each of the metal layers M1 to M4 preferably falls within the range of 5
to 25 nm, and the thickness of each of the intermediate layers N1 to N3
and the protective layer N4 preferably falls within the range of 0.5 to 2
nm.

[0109] For example, each of the metal layers M1 to M4 may be a 10- to
20-nm-thick layer of Au, and each of the intermediate layers N1 to N3 and
the protective layer N4 may be a 0.5- to 1-nm-thick layer of Zr.
Alternatively, each of the metal layers M1 to M4 may be a 5- to
25-nm-thick layer of Au, and each of the intermediate layers N1 to N3 and
the protective layer N4 may be a 0.5- to 2-nm-thick layer of ZrN.

[0110] As shown in FIG. 1 to FIG. 3, the plasmon generator 40 has a groove
40c which opens in the top surface of the multilayer film portion 402 at
a position away from the medium facing surface 60 and receives the second
metal portion 403. The bottom of the groove 40c may be at a higher or
lower level than the top surface of the bonding portion 401B of the first
metal portion 401, or at the same level as the top surface of the bonding
portion 401B. In the example shown in FIG. 1, the bottom of the groove
40c is at the same level as the top surface of the bonding portion 401B,
and the groove 40c penetrates all the layers constituting the multilayer
film portion 402. As shown in FIG. 3, the width of the groove 40c in the
X direction decreases toward the second front end face 40a.

[0111] The second metal portion 403 is received in the groove 40c. The
second metal portion 403 is formed of a metal material. The metal
material used to form the second metal portion 403 may be one of Au, Ag,
Al and Cu, for example. The second metal portion 403 has the function of
enhancing the heat dissipation performance of the plasmon generator 40
and thereby suppressing a temperature rise of the plasmon generator 40.
The second metal portion 403 is not an essential component of the plasmon
generator 40, and can be dispensed with.

[0112] As shown in FIG. 1 and FIG. 3, the plasmon generator 40 includes a
first portion 41 and a second portion 42 adjacent in the Z direction (the
second direction). Note that FIG. 3 depicts the first portion 41 and the
second portion 42 as separate from each other. The first portion 41 is
constituted of the main portion 401A of the first metal portion 401.
Thus, at least part of the first portion 41 is received in the receiving
portion 200. The second portion 42 is constituted of the bonding portion
401B of the first metal portion 401, the multilayer film portion 402 and
the second metal portion 403. The second portion 42 thus includes at
least the first metal layer M1, the second metal layer M2 and the
intermediate layer N1. The dotted line in FIG. 1 also indicates the
boundary between the first portion 41 and the second portion 42.

[0113] The second portion 42 includes the second front end face 40a and
the rear end face 40b. The second front end face 40a has a width in the
range of 5 to 40 nm, for example. No part of the first portion 41 forms
any part of the second front end face 40a.

[0114] The first portion 41 (the main portion 401A) has a bottom surface
opposed to the second region R2, and six side surfaces opposed to a
portion of the second end face 22b of the protruding portion 22 and the
five wall faces of the receiving-portion-forming layer 23 defining the
periphery of the receiving portion 200. The second end face 22b of the
protruding portion 22 is located closer to the medium facing surface 60
than is the first portion 41 of the plasmon generator 40.

[0115] As shown in FIG. 1, FIG. 3 and FIG. 4, the first portion 41
includes a first plasmon exciting portion 40e1 and a second plasmon
exciting portion 40e2. The first plasmon exciting portion 40e1 is formed
of the bottom surface of the first portion 41. The second plasmon
exciting portion 40e2 is formed of one of the six side surfaces of the
first portion 41, the one of the six side surfaces being located closer
to the medium facing surface 60 than is the first plasmon exciting
portion 40e1 (the bottom surface of the first portion 41) and contiguous
with the first plasmon exciting portion 40e1. As shown in FIG. 3 and FIG.
4, the width of the first plasmon exciting portion 40e1 in the X
direction decreases toward the second front end face 40a. The width of
the second plasmon exciting portion 40e2 in the X direction is equal to
that of the first plasmon exciting portion 40e1 at the boundary between
the first and second plasmon exciting portions 40e1 and 40e2, and
gradually decreases toward the second front end face 40a, then becoming
constant.

[0116] The first plasmon exciting portion 40e1 is opposed to the second
region R2 with the cladding layer 24 interposed therebetween. The second
region R2 and the first plasmon exciting portion 40e1 are adjacent in the
Z direction (the second direction). The first plasmon exciting portion
40e1 is perpendicular to the Z direction (the second direction), or
equivalently, parallel to the XY plane.

[0117] The second plasmon exciting portion 40e2 is opposed to the second
end face 22b of the protruding portion 22 with the cladding layer 24
interposed therebetween, and is not exposed in the medium facing surface
60. As shown in FIG. 1, the second plasmon exciting portion 40e2 is
inclined in a similar manner as the second end face 22b. More
specifically, the second plasmon exciting portion 40e2 has a third edge
E3 in contact with the first plasmon exciting portion 40e1, and a fourth
edge E4 in contact with the second portion 42 of the plasmon generator
40. The fourth edge E4 is located closer to the first front end face 20a
of the core 20 than is the third edge E3. The distance from the medium
facing surface 60 to an arbitrary point on the second plasmon exciting
portion 40e2 decreases with increasing distance from the arbitrary point
to the third edge E3. With respect to the Z direction (the second
direction), the second plasmon exciting portion 40e2 preferably forms an
angle in the same range as the preferred range of the angle that the
second end face 22b forms with respect to the Z direction (the second
direction).

[0118] In FIG. 1, FIG. 3 and FIG. 4, the symbol 41a represents one of the
side surfaces of the first portion 41, the one being located farther from
the medium facing surface 60 than is the first plasmon exciting portion
40e1 (the bottom surface of the first portion 41) and contiguous with the
first plasmon exciting portion 40e1. The side surface 41a is opposed to
the wall face 23b with the cladding layer 24 interposed therebetween.
Like the wall face 23b, the side surface 41a may be perpendicular to the
Y direction or inclined with respect to the Z direction (the second
direction). Where the side surface 41a is inclined with respect to the Z
direction, the distance from the medium facing surface 60 to an arbitrary
point on the side surface 41a decreases with increasing distance from the
arbitrary point to the top surface of the first portion 41, that is, with
decreasing distance from the arbitrary point to the top surface 1a of the
substrate 1. FIG. 1 to FIG. 3 show an example in which the side surface
41a is inclined with respect to the Z direction.

[0119] As shown in FIG. 3 and FIG. 4, the second portion 42 includes a
narrow portion located near the medium facing surface 60, and a wide
portion which is located farther from the medium facing surface 60 than
is the narrow portion. The width of the narrow portion in the X direction
may be constant regardless of distance from the medium facing surface 60,
or may decrease toward the medium facing surface 60. The width of the
wide portion in the X direction is equal to that of the narrow portion at
the boundary position between the narrow portion and the wide portion,
and is greater than that of the narrow portion in the other positions.

[0120] The cladding layer 24 includes an interposition portion 24a
interposed between a combination of the second region R2 and the second
end face 22b of the protruding portion 22 and a combination of the first
and second plasmon exciting portions 40e1 and 40e2. Since the cladding
layer 24 is part of the cladding, the cladding can be said to include the
interposition portion 24a. The interposition portion 24a has a thickness
within the range of, for example, 10 to 100 nm, and preferably within the
range of 20 to 30 nm.

[0121] Now, the principle of generation of near-field light in the present
embodiment and the principle of thermally-assisted magnetic recording
using near-field light will be described in detail. Laser light emitted
from a laser diode (not illustrated) enters the incidence end of the main
body portion 21 of the core 20. As shown in FIG. 5, the laser light 50
propagates through the main body portion 21 of the core 20 toward the
medium facing surface 60, and reaches the vicinity of the plasmon
generator 40. Each of the second region R2 and the second end face 22b of
the protruding portion 22 generates evanescent light based on the laser
light 50 propagating through the core 20 (the main body portion 21). More
specifically, when the laser light 50 is totally reflected at the second
region R2, the second region R2 generates first evanescent light
permeating into the interposition portion 24a. When the laser light 50 is
totally reflected at the second end face 22b of the protruding portion
22, the second end face 22b of the protruding portion 22 generates second
evanescent light permeating into the interposition portion 24a.

[0122] In the plasmon generator 40, first surface plasmons are excited on
the first plasmon exciting portion 40e1 through coupling with the first
evanescent light. Second surface plasmons are excited on the second
plasmon exciting portion 40e2 through coupling with the second evanescent
light. The first and second surface plasmons propagate along the surfaces
of the first and second portions 41 and 42 to reach the second front end
face 40a. As a result, the first and second surface plasmons concentrate
at the second front end face 40a, and near-field light is generated from
the second front end face 40a based on the first and second surface
plasmons.

[0123] The near-field light generated from the second front end face 40a
is projected toward the recording medium 80, reaches the surface of the
recording medium 80 and heats a part of the magnetic recording layer of
the recording medium 80. This lowers the coercivity of the part of the
magnetic recording layer. In thermally-assisted magnetic recording, the
part of the magnetic recording layer with the lowered coercivity is
subjected to a write magnetic field produced by the main pole 29, whereby
data is written.

[0124] A method of manufacturing the thermally-assisted magnetic recording
head according to the present embodiment will now be described. The
method of manufacturing the thermally-assisted magnetic recording head
includes the steps of forming components of a plurality of
thermally-assisted magnetic recording heads, except the substrates 1, on
a wafer that includes portions to become the substrates 1 of the
plurality of thermally-assisted magnetic recording heads, thereby
fabricating a substructure including a plurality pre-head portions
arranged in rows, the plurality of pre-head portions becoming individual
thermally-assisted magnetic recording heads later; and cutting the
substructure to separate the plurality of pre-head portions from each
other and forming the medium facing surface 60 for each of the plurality
of pre-head portions (this step will be referred to as the step of
forming the medium facing surface 60). A plurality of thermally-assisted
magnetic recording heads are produced in this manner.

[0125] The method of manufacturing the thermally-assisted magnetic
recording head according to the present embodiment will be described in
more detail below with attention focused on a single thermally-assisted
magnetic recording head. The following descriptions include the
description of a method of manufacturing the near-field light generator
according to the present embodiment. The method of manufacturing the
thermally-assisted magnetic recording head first forms the insulating
layer 2, the bottom shield layer 3, and the bottom shield gap film 4 in
this order on the substrate 1. Next, the MR element 5 and two leads (not
illustrated) connected to the MR element 5 are formed on the bottom
shield gap film 4. The top shield gap film 6 is then formed to cover the
MR element 5 and the leads. Next, the top shield layer 7, the insulating
layer 8, the middle shield layer 9, and the nonmagnetic layer 10 are
formed in this order on the top shield gap film 6.

[0126] Then, the return pole layer 11 is formed on the nonmagnetic layer
10. Next, an insulating layer (not illustrated) is formed to cover the
return pole layer 11. The non-illustrated insulating layer is then
polished by, for example, chemical mechanical polishing (hereinafter
referred to as CMP), until the return pole layer 11 is exposed. Next, the
insulating layer 14 is formed over the return pole layer 11 and the
non-illustrated insulating layer. The insulating layer 14 is then
selectively etched to form therein two openings for exposing the top
surface of the return pole layer 11. The shield layer 12 and the coupling
layer 13 are then formed on the return pole layer 11 at the positions of
the two openings. Next, the coil 15 is formed on the insulating layer 14.

[0127] Next, the insulating layer 16 is formed over the entire top surface
of the stack. The insulating layer 16 is then polished by, for example,
CMP, until the shield layer 12, the coupling layer 13 and the coil 15 are
exposed. Next, although not illustrated, the first layers of the coupling
portions 17A and 17B are formed on the coupling layer 13. Then, the
cladding layer 18 is formed over the entire top surface of the stack. The
cladding layer 18 is then polished by, for example, CMP, until the first
layers of the coupling portions 17A and 17B are exposed.

[0128] Next, the main body portion 21 of the core 20 is formed on the
cladding layer 18. The main body portion 21 is formed by, for example,
first forming a dielectric layer over the entire top surface of the stack
and then patterning the dielectric layer by etching a portion of the
dielectric layer by reactive ion etching (hereinafter referred to as
RIE). Next, although not illustrated, the second layers of the coupling
portions 17A and 17B are formed on the first layers of the coupling
portions 17A and 17B, respectively. Next, the cladding layer 19 is formed
over the entire top surface of the stack. The cladding layer 19 is then
polished by, for example, CMP, until the main body portion 21 and the
second layers of the coupling portions 17A and 17B are exposed.

[0129] Reference is now made to FIG. 7 to FIG. 16 to describe steps to be
performed after the polishing of the cladding layer 19 up to the
formation of the plasmon generator 40. FIG. 7 to FIG. 16 each illustrate
a stack of layers formed in the process of manufacturing the
thermally-assisted magnetic recording head. FIGS. 7 to 12 and 16 each
show a cross section that intersects the end face 29a of the main pole 29
and that is perpendicular to the medium facing surface 60 and to the top
surface 1a of the substrate 1. Note that portions located below the main
body portion 21 are omitted from FIGS. 7 to 12 and 16. FIG. 15 is a plan
view of the stack. In FIGS. 7 to 12, 15 and 16, the symbol "ABS"
indicates the position at which the medium facing surface 60 is to be
formed. FIGS. 13 and 14 each show a cross section parallel to the
position ABS.

[0130] FIG. 7 shows a step that follows the polishing of the cladding
layer 19. In this step, first, a photoresist mask 71 is formed on the top
surface of the stack. The photoresist mask 71 has an opening 71a shaped
to correspond to the shape of the protruding portion 22 to be formed
later, and covers the second and third regions R2 and R3 (see FIG. 1 and
FIG. 2) of the first surface 21b of the main body portion 21. The opening
71a of the photoresist mask 71 includes an inclined portion to define the
shape of the second end face 22b of the protruding portion 22 to be
formed later. Next, a dielectric layer 22P of a dielectric material that
is to form the protruding portion 22 is formed on the top surface of the
stack. The dielectric layer 22P is formed on a part of the first surface
21b of the main body portion 21 other than the second and third regions
R2 and R3. This part of the first surface 21b includes the first region
R1. The dielectric layer 22P is formed also on the photoresist mask 71.
Next, the photoresist mask 71 is lifted off. As a result, the remainder
of the dielectric layer 22P on the first surface 21b of the main body
portion 21 becomes the protruding portion 22, and the core 20 is thereby
completed.

[0131] FIG. 8 shows the next step. In this step, first, a dielectric layer
23P of a dielectric material that is to form the
receiving-portion-forming layer 23 is formed over the entire top surface
of the stack. The dielectric layer 23P is then polished by, for example,
CMP, until the protruding portion 22 is exposed. The top surface 22c of
the protruding portion 22 and the top surface of the dielectric layer 23P
are thereby made even with each other.

[0132] FIG. 9 shows the next step. In this step, first, a photoresist mask
72 is formed on the dielectric layer 23P. The photoresist mask 72 covers
the dielectric layer 23P except a portion thereof where the receiving
portion 200 is to be formed. Using the photoresist mask 72, the
dielectric layer 23P is then taper-etched by, for example, RIE, so that
the receiving portion 200 is formed. This etching is performed under such
conditions that the materials to form the main body portion 21 and the
protruding portion 22 are not etched at all or are hardly etched whereas
the material to form the receiving-portion-forming layer 23 is
selectively etched. This etching proceeds until the first surface 21b of
the main body portion 21 is exposed. A portion of the dielectric layer
23P that remains after this etching becomes the receiving-portion-forming
layer 23. The photoresist mask 72 is then removed.

[0133] FIG. 10 shows the next step. In this step, first, the cladding
layer 24 and the adhesion layer 39 are formed in this order over the
entire top surface of the stack. Then, a metal film 401P is formed on the
adhesion layer 39 by sputtering, for example. The metal film 401P will
later become the first metal portion 401 of the plasmon generator 40. The
metal film 401P is formed such that the top surface of its portion
received in the receiving portion 200 is higher in level than the top
surface of the first metal portion 401 to be formed later. Then, the
metal film 401P is polished by, for example, CMP, until the top surface
of the metal film 401P reaches the level of the top surface of the first
metal portion 401 (the top surface of the bonding portion 401B) to be
formed later. Next, a plurality of films that will later become the
layers of the multilayer film portion 402 of the plasmon generator 40 are
formed in succession on the metal film 401P by sputtering, for example. A
multilayer film 402P composed of the plurality of films is thereby
formed.

[0134] FIG. 11 shows the next step. In this step, first, an etching mask
(not illustrated) is formed on the multilayer film 402P. The
non-illustrated etching mask covers a portion of the multilayer film 402P
that is located closer to the position ABS, which is the position at
which the medium facing surface 60 is to be formed, than to the rear end
face 40b of the plasmon generator 40 to be formed later. Next, portions
of the adhesion layer 39, the metal film 401P and the multilayer film
402P other than their portions lying under the non-illustrated etching
mask are removed by ion beam etching (hereinafter referred to as IBE),
for example. The non-illustrated etching mask is then removed.

[0135] FIG. 12 shows the next step. In this step, the multilayer film 402P
is etched by, for example, IBE, to thereby form the groove 40c to receive
the second metal portion 403 to be formed later.

[0136] FIG. 13 shows the next step. FIG. 13 illustrates a cross section
that is parallel to the position ABS and that intersects the groove 40c.
In this step, first, a photoresist mask (not illustrated) having an
opening shaped to correspond to the planar shape of the plasmon generator
40 is formed on the top surface of the stack. Next formed is a metal film
403P which will later become the second metal portion 403 of the plasmon
generator 40. The metal film 403P is formed to fill the groove 40c and to
have a top surface located at a higher level than the top surface of the
multilayer film 402P. Next, a dielectric layer 73 of a dielectric
material is formed over the entire top surface of the stack. The
non-illustrated photoresist mask is then lifted off.

[0137] FIG. 14 shows the next step. FIG. 14 illustrates a cross section
taken at the same position as FIG. 13. In this step, first, the metal
film 403P and the dielectric layer 73 are polished by, for example, CMP,
until the top surface of the multilayer film 402P is exposed. This makes
the metal film 403P into the second metal portion 403. Then, the polished
surface is slightly etched by IBE, for example.

[0138] FIG. 15 and FIG. 16 show the next step. FIG. 16 is a
cross-sectional view showing a cross section taken along line 16-16 in
FIG. 15. In this step, first, an etching mask (not illustrated) whose
planar shape corresponds to the planar shape of the plasmon generator 40
is formed on the top surface of the stack. Then, portions of the adhesion
layer 39, the metal film 401P and the multilayer film 402P other than
their portions lying under the non-illustrated etching mask are removed
by IBE, for example. The plasmon generator 40 and the near-field light
generator are thereby completed. In FIG. 16, the boundary between the
first portion 41 and the second portion 42 of the plasmon generator 40 is
indicated in a dotted line. As shown in FIG. 16, at least part of the
first portion 41 is formed to be received in the receiving portion 200.
The non-illustrated etching mask is then removed.

[0139] As has been described, the method of manufacturing the near-field
light generator according to the present embodiment includes the steps of
forming the core 20; forming the cladding; and forming the plasmon
generator 40 after the step of forming the core 20. The step of forming
the core 20 includes the step of forming the main body portion 21 and the
step of forming the protruding portion 22 on the first region R1 of the
first surface 21b of the main body portion 21. The step of forming the
cladding includes the step of forming the receiving-portion-forming layer
23 before the step of forming the plasmon generator 40.

[0140] Now, steps to follow the step shown in FIG. 15 and FIG. 16 will be
described with reference to FIG. 5 and FIG. 6. First, the dielectric
layer 25 is formed over the entire top surface of the stack. The
dielectric layer 25 is then polished by, for example, CMP, until the
plasmon generator' 40 is exposed. Next, the heat sink 26 is formed on the
plasmon generator 40 and the dielectric layer 25. The dielectric layer 27
is then formed to cover the heat sink 26. The dielectric layer 28 is then
formed to cover the dielectric layer 27.

[0141] The receiving-portion-forming layer 23, the cladding layer 24 and
the dielectric layers 25, 27 and 28 are then selectively etched to form
therein two openings for exposing the respective top surfaces of the
second layers of the coupling portions 17A and 17B. Next, the third
layers of the coupling portions 17A and 17B are formed on the second
layers of the coupling portions 17A and 17B, respectively. Then, the main
pole 29 is formed on the dielectric layer 28, and the coupling layer 30
is formed on the third layers of the coupling portions 17A and 17B and
the dielectric layer 28. Next, the dielectric layer 31 is formed over the
entire top surface of the stack. The dielectric layer 31 is then polished
by, for example, CMP, until the main pole 29 and the coupling layer 30
are exposed. The top surfaces of the main pole 29, the coupling layer 30
and the dielectric layer 31 are thereby made even with each other.

[0142] Next, the coil 32 is formed on the dielectric layer 31. The
insulating layer 33 is then formed to cover the coil 32. Next, the yoke
layer 34 is formed over the main pole 29, the coupling layer 30 and the
insulating layer 33. Then, the protective layer 35 is formed to cover the
yoke layer 34. Wiring, terminals, and other components are then formed on
the top surface of the protective layer 35. When the substructure is
completed thus, the step of forming the medium facing surface 60 is
performed. A protective film for covering the medium facing surface 60
may be formed thereafter. Being provided with the medium facing surface
60, each pre-head portion becomes a thermally-assisted magnetic recording
head.

[0143] The step of forming the medium facing surface 60 includes the step
of polishing the surface that is formed for each pre-head portion by
cutting the substructure, and the step of forming a rail on the polished
surface for allowing the slider to fly.

[0144] In the aforementioned polishing step, the layers exposed in the
medium facing surface 60 may be polished in different amounts due to
differences between materials used for those layers, and this may cause
irregularities on the medium facing surface 60.

[0145] Further, in the aforementioned polishing step, polishing residues
of the metal materials may grow to cause smears. In order to remove the
smears, the step of forming the medium facing surface 60 may include the
step of etching the polished surface slightly by, for example, IBE, after
the polishing step.

[0146] The effects of the near-field light generator and the
thermally-assisted magnetic recording head according to the present
embodiment will now be described. In the present embodiment, the plasmon
generator 40 includes the first portion 41 and the second portion 42. The
second portion 42 includes the second front end face 40a of the plasmon
generator 40. The first portion 41 includes the first and second plasmon
exciting portions 40e1 and 40e2. The present embodiment allows the
dimension of the second front end face 40a in the Z direction and the
area of the second front end face 40a to be smaller than in the case
where the thickness of the entire plasmon generator and the dimension of
the front end face of the plasmon generator in the Z direction are equal.
Consequently, the present embodiment makes it possible to increase the
volume and the surface area of the first portion 41 to allow a lot of
surface plasmons to be excited on the plasmon generator 40 without
increasing the area of the second front end face 40a.

[0147] Further, since the second front end face 40a is allowed to have a
small area, it is possible to prevent the second front end face 40a from
being significantly recessed relative to the other parts of the medium
facing surface 60 in the step of forming the medium facing surface 60.
The present embodiment thus makes it possible to prevent degradation in
heating performance of the plasmon generator 40 that would occur where
the second front end face 40a is significantly recessed relative to the
other parts of the medium facing surface 60. Moreover, since the second
front end face 40a is allowed to have a small area, it is possible to
prevent the plasmon generator 40 from expanding and significantly
protruding toward the recording medium 80 when the plasmon generator 40
increases in temperature. The present embodiment thus makes it possible
to prevent damage to the recording medium 80, breakage of the plasmon
generator 40 or the protective film covering the medium facing surface
60, and corrosion of the plasmon generator 40.

[0148] Further, in the present embodiment, since the first portion 41 does
not include the second front end face 40a of the plasmon generator 40,
the material for the first portion 41 can be selected from any metal
materials that have high electrical conductivity suitable for excitation
and propagation of surface plasmons, without the need for considering
mechanical strength. This allows for appropriate excitation and
propagation of surface plasmons on the first portion 41.

[0149] Further, in the present embodiment, the second portion 42 includes
at least the first metal layer M1, the second metal layer M2 and the
intermediate layer N1. The intermediate layer N1 is interposed between
the first metal layer M1 and the second metal layer M2. The intermediate
layer N1 is formed of a material that is higher in Vickers hardness than
the metal material used to form the first metal layer M1 and the metal
material used to form the second metal layer M2. This makes it possible
to prevent the first metal layer M1 and the second metal layer M2
sandwiching the intermediate layer N1 from being deformed. Further, the
present embodiment allows the second portion 42 as a whole to be higher
in mechanical strength than in a case where the second portion consists
only of a single metal layer formed of the metal layer material described
previously. Consequently, the present embodiment makes it possible to
prevent the second portion 42 from being deformed or damaged, and the
second front end face 40a from being significantly recessed relative to
the other parts of the medium facing surface 60 in the step of forming
the medium facing surface 60 or due to a temperature change of the
plasmon generator 40.

[0150] The above-described effects become more noticeable when the second
portion 42 includes one or more pairs of an intermediate layer and a
metal layer in addition to the first metal layer M1, the second metal
layer M2 and the intermediate layer N1.

[0151] Further, in the present embodiment, the core 20 includes the main
body portion 21 and the protruding portion 22. The first and second
surfaces 21b and 21c of the main body portion 21 are flat surfaces
parallel to each other, and the first surface 21b includes the second
region R2 to generate the first evanescent light. The thickness (the
dimension in the Z direction) of the main body portion 21 is constant
regardless of the distance from the incidence end of the main body
portion 21, and the center of the main body portion 21 in the thickness
direction coincides with the center of the incidence end of the main body
portion 21 in the thickness direction. Consequently, when the laser light
50 has entered the incidence end of the main body portion 21 with the
optical axis of the laser light 50 aligned with the center of the
incidence end in the thickness direction, the optical axis coincides with
the center of the main body portion 21 in the thickness direction
regardless of the distance from the incidence end of the main body
portion 21. Thus, in the present embodiment, there is no reduction in
efficiency of propagation of the laser light 50 resulting from a
misalignment occurring between the optical axis of the laser light 50 and
the center of the main body portion 21 in the thickness direction in the
course of travel of the laser light 50 to reach the second region R2. The
present embodiment thus allows a larger amount of first evanescent light
to be generated from the second region R2, thereby allowing a lot of
first surface plasmons to be excited on the first plasmon exciting
portion 40e1 of the plasmon generator 40.

[0152] Further, the present embodiment allows the second evanescent light
to be generated from the second end face 22b of the protruding portion 22
of the core 20 and allows the second surface plasmons to be excited on
the second plasmon exciting portion 40e2 of the plasmon generator 40.
Thus, in the present embodiment, it is possible to excite a larger amount
of surface plasmons on the plasmon generator 40 than in the case without
the protruding portion 22.

[0153] Consequently, the present embodiment makes it possible to provide a
near-field light generator that allows a lot of surface plasmons to be
excited on the plasmon generator 40 and allows the plasmon generator 40
to operate with high reliability, and to provide a thermally-assisted
magnetic recording head including such a near-field light generator.

[0154] Where the intermediate layer material is a metal material and the
metal layer material is higher in electrical conductivity than the
intermediate layer material, the intermediate layers N1 to N3 are
preferably smaller in thickness than the metal layers M1 to M4. In such a
case, it is possible to reduce loss of surface plasmons when the surface
plasmons propagate from the end of the metal layer M1 located in the
second front end face 40a to the respective ends of the metal layers M2
to M4 located in the second front end face 40a.

[0155] The surface plasmons need not necessarily propagate to the
respective ends of the metal layers M3 and M4 and the intermediate layers
N2 and N3 located in the second front end face 40a. Even in such a case,
the metal layers M3 and M4 and the intermediate layers N2 and N3
contribute to the enhancement of the mechanical strength of the plasmon
generator 40 as a whole.

[0156] Further, the following effects are provided where a metal layer is
sandwiched between two intermediate layers in the plasmon generator 40. A
metal layer is typically formed of a metal polycrystal. In general, when
a metal polycrystal gets hot, a plurality of crystal grains constituting
the metal polycrystal aggregate and grow, and can thereby cause the metal
polycrystal to be deformed. If a metal layer is sandwiched between two
intermediate layers, the metal layer is restrained to some extent by the
two intermediate layers. Thus, in such a case, it is possible to prevent
the aggregation and growth of the plurality of crystal grains
constituting the metal layer (the metal polycrystal) when the metal layer
gets hot. This consequently allows for preventing the metal layer from
becoming deformed.

[0157] In the present embodiment, the second end face 22b of the
protruding portion 22 and the second plasmon exciting portion 40e2 are
both inclined with respect to the medium facing surface 60. In the second
plasmon exciting portion 40e2, the fourth edge E4 is located closer to
the first front end face 20a of the core 20 than is the third edge E3.
This configuration allows the first surface plasmons excited on the first
plasmon exciting portion 40e1 and the second surface plasmons excited on
the second plasmon exciting portion 40e2 to propagate through the second
plasmon exciting portion 40e2 to reach the vicinity of the second front
end face 40a.

[0158] It should be noted that if the second end face 22b of the
protruding portion 22 and the second plasmon exciting portion 40e2 are
parallel to the medium facing surface 60, it becomes difficult to excite
the second surface plasmons on the second plasmon exciting portion 40e2,
and the first surface plasmons suffer a great loss when they propagate to
the second front end face 40a. In the present embodiment, since the
second end face 22b of the protruding portion 22 and the second plasmon
exciting portion 40e2 are inclined with respect to the medium facing
surface 60 as mentioned above, it is possible to excite the second
surface plasmons on the second plasmon exciting portions 40e2 and to
reduce loss of the first surface plasmons when they propagate to the
second front end face 40a.

[0159] Consequently, the present embodiment allows the first surface
plasmons excited on the first plasmon exciting portion 40e1 and the
second surface plasmons excited on the second plasmon exciting portion
40e2 to propagate efficiently to the second front end face 40a. The
above-described effect is reduced if the angle formed by each of the
second end face 22b and the second plasmon exciting portion 40e2 with
respect to the Z direction (the second direction) is close to 0°.
On the other hand, if the aforementioned angle is excessively close to
90°, it becomes difficult to form the second end face 22a and the
second plasmon exciting portion 40e2. In view of this, the aforementioned
angle is preferably in the range of 45° to 80°.

[0160] To allow the first surface plasmons excited on the first plasmon
exciting portion 40e1 and the second surface plasmons excited on the
second plasmon exciting portion 40e2 to propagate efficiently to the
second front end face 40a, the fourth edge E4 of the second plasmon
exciting portion 40e2 is preferably as close as possible to the second
front end face 40a, and is more preferably located in the second front
end face 40a. To achieve this, the second edge E2 of the second end face
22b of the protruding portion 22 is preferably as close as possible to
the first front end face 20a of the core 20, and is more preferably
located in the first front end face 20a.

Second Embodiment

[0161] A method of manufacturing a thermally-assisted magnetic recording
head according to a second embodiment of the invention will now be
described with reference to FIG. 17 and FIG. 18. The following
descriptions include the description of a method of manufacturing a
near-field light generator according to the present embodiment. FIG. 17
and FIG. 18 each illustrate a stack of layers formed in the process of
manufacturing the thermally-assisted magnetic recording head. FIG. 17 and
FIG. 18 each show a cross section that intersects the end face 29a of the
main pole 29 and that is perpendicular to the medium facing surface 60
and to the top surface 1a of the substrate 1 (see FIG. 5 and FIG. 6). In
FIG. 17 and FIG. 18, the symbol "ABS" indicates the position at which the
medium facing surface 60 is to be formed.

[0162] The method of manufacturing the thermally-assisted magnetic
recording head according to the present embodiment is the same as the
method according to the first embodiment up to the step of polishing the
cladding layer 19 (see FIG. 6). FIG. 17 shows the next step. This step
forms an initial protruding portion 22P which will later become the
protruding portion 22 of the core 20. The initial protruding portion 22P
is formed on a part of the first surface 21b of the main body portion 21
of the core 20 other than the second and third regions R2 and R3 (see
FIG. 1 and FIG. 2). This part of the first surface 21b includes the first
region R1.

[0163] FIG. 18 shows the next step. In this step, first, an etching mask
(not illustrated) is formed on the top surface of the stack. Either a
photoresist mask or a hard mask is used as this etching mask. This
etching mask does not cover a region of the initial protruding portion
22P where the second end face 22b of the protruding portion 22 is to be
formed later. Using this etching mask, the initial protruding portion 22P
is then taper-etched by, for example, IBE, so as to provide the initial
protruding portion 22P with the second end face 22b. This makes the
initial protruding portion 22P into the protruding portion 22, and
thereby completes the core 20. The non-illustrated etching mask is then
removed. The subsequent steps are the same as those in the first
embodiment.

[0164] As described above, the step of forming the protruding portion 22
in the method of manufacturing the near-field light generator according
to the present embodiment includes the step of forming the initial
protruding portion 22P on the first region R1 of the first surface 21b of
the main body portion 21, and the step of taper-etching the initial
protruding portion 22 so that the initial protruding portion 22P is
provided with the second end face 22b and thereby becomes the protruding
portion 22. The remainder of configuration, function and effects of the
present embodiment are similar to those of the first embodiment.

Third Embodiment

[0165] A near-field light generator and a thermally-assisted magnetic
recording head according to a third embodiment of the invention will now
be described. First, reference is made to FIG. 19 to describe the
configurations of the near-field light generator and the
thermally-assisted magnetic recording head according to the present
embodiment. FIG. 19 is a cross-sectional view showing the main part of
the thermally-assisted magnetic recording head according to the present
embodiment.

[0166] The near-field light generator and the thermally-assisted magnetic
recording head according to the present embodiment differ from those
according to the first embodiment in the following ways. In the present
embodiment, as shown in FIG. 19, the waveguide includes a core 120 in
place of the core 20. The location of the core 120 is the same as that of
the core 20. The cladding layers 18 and 19 (see FIG. 5 and FIG. 6), the
cladding layer 24 and the receiving-portion-forming layer 23 are disposed
around the core 120. The core 120 is formed of the same material as the
core 20.

[0167] The core 120 has a first front end face 120a lying at an end of the
core 120 in the direction of travel of the laser light 50 (see FIG. 5)
(the first direction). In the present embodiment, the first front end
face 120a is located in the medium facing surface 60. Further, the core
120 includes a main body portion 121 and a protruding portion 122
adjacent in the Z direction (the second direction). In FIG. 19, the
boundary between the main body portion 121 and the protruding portion 122
is indicated in a broken line. The main body portion 121 and the
protruding portion 122 are shaped like the main body portion 21 and the
protruding portion 22 of the core 20, respectively. In the present
embodiment, however, the main body portion 121 and the protruding portion
122 are integrally formed as described later.

[0168] As shown in FIG. 19, the main body portion 121 has: an end face
121a constituting part of the first front end face 120a; a first surface
121b which is a top surface facing toward the plasmon generator 40; a
second surface 121c opposite to the first surface 121b; two side surfaces
(not illustrated); and an incidence end (not illustrated). The first and
second surfaces 121b and 121c are flat surfaces parallel to each other.
Both of the first and second surfaces 121b and 121c are perpendicular to
the Z direction (the second direction), or equivalently, parallel to the
XY plane.

[0169] As shown in FIG. 19, the first surface 121b includes a first region
R1, a second region R2 and a third region R3. The first to third regions
R1 to R3 of the present embodiment are shaped and located in the same
manner as the first to third regions R1 to R3 of the first embodiment.

[0170] As shown in FIG. 19, the protruding portion 122 lies on the first
region R1 of the first surface 121b. The protruding portion 122 has: a
first end face 122a constituting part of the first front end face 120a; a
second end face 122b opposite to the first end face 122a; a top surface
122c; and two side surfaces (not illustrated). The second end face 122b
is inclined with respect to the medium facing surface 60. More
specifically, as shown in FIG. 19, the second end face 122b has a first
edge E1 in contact with the first surface 121b of the main body portion
121, and a second edge E2 farthest from the first surface 121b. The
second edge E2 is located closer to the first front end face 120a of the
core 120 than is the first edge E1. The distance from the medium facing
surface 60 to an arbitrary point on the second end face 122b decreases
with increasing distance from the arbitrary point to the first edge E1.
With respect to the Z direction (the second direction), the second end
face 122b preferably forms an angle in the same range as the preferred
range of the angle that the second end face 22b described in the first
embodiment section forms with respect to the Z direction (the second
direction).

[0171] In the present embodiment, the receiving portion 200 is defined by
the protruding portion 122 and the receiving-portion-forming layer 23.
Portions of the receiving-portion-forming layer 23 located on opposite
sides of the second region R2 of the first surface 121b in the X
direction are in contact with portions of the second end face 122b of the
protruding portion 122. Another portion of the second end face 122b of
the protruding portion 122 is covered with the cladding layer 24.

[0172] Each of the second region R2 of the first surface 121b and the
second end face 122b of the protruding portion 122 generates evanescent
light based on the laser light 50 propagating through the core 120 (the
main body portion 121). More specifically, when the laser light 50 is
totally reflected at the second region R2, the second region R2 generates
first evanescent light permeating into the interposition portion 24a of
the cladding layer 24. When the laser light 50 is totally reflected at
the second end face 122b of the protruding portion 122, the second end
face 122b of the protruding portion 122 generates second evanescent light
permeating into the interposition portion 24a of the cladding layer 24.

[0173] A method of manufacturing the thermally-assisted magnetic recording
head according to the present embodiment will now be described with
reference to FIG. 20 and FIG. 21. The following descriptions include the
description of a method of manufacturing the near-field light generator
according to the present embodiment. FIG. 20 and FIG. 21 each illustrate
a stack of layers formed in the process of manufacturing the
thermally-assisted magnetic recording head. FIG. 20 and FIG. 21 each show
a cross section that intersects the end face 29a of the main pole 29 and
that is perpendicular to the medium facing surface 60 and to the top
surface 1a of the substrate 1 (see FIG. 5 and FIG. 6). In FIG. 20 and
FIG. 21, the symbol "ABS" indicates the position at which the medium
facing surface 60 is to be formed.

[0174] The method of manufacturing the thermally-assisted magnetic
recording head according to the present embodiment is the same as the
method according to the first embodiment up to the step of polishing the
cladding layer 18 (see FIG. 5 and FIG. 6). FIG. 20 shows the next step.
In this step, first, an initial core 120P having a top surface 120Pa is
formed on the cladding layer 18. The initial core 120P will later become
the core 120. The initial core 120P is formed by, for example, first
forming a dielectric layer over the entire top surface of the stack and
then patterning the dielectric layer by etching a portion of the
dielectric layer by RIE. Next, the second layers of the coupling portions
17A and 17B are formed on the first layers of the coupling portions 17A
and 17B (see FIG. 5), respectively. Next, the cladding layer 19 (see FIG.
6) is formed over the entire top surface of the stack. The cladding layer
19 is then polished by, for example, CMP, until the top surface 120Pa of
the initial core 120P and top surfaces of the second layers of the
coupling portions 17A and 17B are exposed.

[0175] FIG. 21 shows the next step. In this step, first, an etching mask
(not illustrated) is formed on the top surface of the stack. Either a
photoresist mask or a hard mask is used as this etching mask. This
etching mask does not cover a region of the top surface 120Pa of the
initial core 120P where the second end face 122b of the protruding
portion 122 is to be formed later and regions of the top surface 120Pa of
the initial core 120P where the second and third regions R2 and R3 of the
first surface 121b of the main body portion 121 are to be formed later.
Using this etching mask, the top surface 120Pa of the initial core 120P
is then partly etched by, for example, IBE, so that the second end face
122b and the second and third regions R2 and R3 of the first surface 121b
are formed. The core 120 is thereby completed. As shown in FIG. 20 and
FIG. 21, the main body portion 121 and the protruding portion 122 are
integrally formed from the initial core 120P. In FIG. 21, the boundary
between the main body portion 121 and the protruding portion 122 is
indicated in a broken line. The non-illustrated etching mask is then
removed. The subsequent steps are the same as those in the first
embodiment.

[0176] As described above, the step of forming the core 120 in the method
of manufacturing the near-field light generator according to the present
embodiment includes the step of forming the initial core 120P having the
top surface 120Pa, and the step of partly etching the top surface 120Pa
of the initial core 120P so that the initial core 120P becomes the core
120. The remainder of configuration, function and effects of the present
embodiment are similar to those of the first embodiment.

Fourth Embodiment

[0177] A near-field light generator and a thermally-assisted magnetic
recording head according to a fourth embodiment of the invention will now
be described. First, reference is made to FIG. 22 to describe the
configurations of the near-field light generator and the
thermally-assisted magnetic recording head according to the present
embodiment. FIG. 22 is a cross-sectional view showing the main part of
the thermally-assisted magnetic recording head according to the present
embodiment.

[0178] The near-field light generator and the thermally-assisted magnetic
recording head according to the present embodiment differ from those
according to the first embodiment in the following ways. In the present
embodiment, the cladding layer 24 covers the second and third regions R2
and R3 of the first surface 21b of the main body portion 21 of the core
20 and the second end face 22b and the top surface 22c of the protruding
portion 22 of the core 20. The receiving-portion-forming layer 23 is
disposed over the third region R3 with the cladding layer 24 interposed
between the third region R3 and the receiving-portion-forming layer 23.
The top surface 23a of the receiving-portion-forming layer 23 is located
at the same level as the top surface of the first metal portion 401 (the
top surface of the bonding portion 401B) of the plasmon generator 40. The
dielectric layer 25 lies on the receiving-portion-forming layer 23.

[0179] As described in the first embodiment section, the
receiving-portion-forming layer 23 has five wall faces defining the
periphery of the receiving portion 200. In FIG. 22, the symbol 23b
represents one of the five wall faces of the receiving-portion-forming
layer 23 that is located farther from the medium facing surface 60 than
is the second region R2. In the present embodiment, this wall face 23b is
perpendicular to the Y direction, or equivalently, parallel to the medium
facing surface 60.

[0180] In FIG. 22, the symbol 41a represents one of the side surfaces of
the first portion 41 of the plasmon generator 40, the one being located
farther from the medium facing surface 60 than is the first plasmon
exciting portion 40e1 of the first portion 41 (the bottom surface of the
first portion 41) and contiguous with the first plasmon exciting portion
40e1. The side surface 41a is in contact with the wall face 23b. Like the
wall face 23b, the side surface 41a is perpendicular to the Y direction,
or equivalently, parallel to the medium facing surface 60.

[0181] The waveguide of the present embodiment may include the core 120
described in the third embodiment section, in place of the core 20.

[0182] A method of manufacturing the thermally-assisted magnetic recording
head according to the present embodiment will now be described with
reference to FIG. 23 to FIG. 25. The following descriptions include the
description of a method of manufacturing the near-field light generator
according to the present embodiment. FIG. 23 to FIG. 25 each illustrate a
stack of layers formed in the process of manufacturing the
thermally-assisted magnetic recording head. FIG. 23 to FIG. 25 each show
a cross section that intersects the end face 29a of the main pole 29 and
that is perpendicular to the medium facing surface 60 and to the top
surface 1a of the substrate 1 (see FIG. 5 and FIG. 6). In FIG. 23 to FIG.
25, the symbol "ABS" indicates the position at which the medium facing
surface 60 is to be formed.

[0183] The method of manufacturing the thermally-assisted magnetic
recording head according to the present embodiment is the same as the
method according to the first or second embodiment up to the step of
forming the core 20. FIG. 23 shows the next step. In this step, first,
the cladding layer 24 and the adhesion layer 39 are formed in this order
over the entire top surface of the stack. Then, a metal film 401P is
formed on the adhesion layer 39 by sputtering, for example. The metal
film 401P will later become the first metal portion 401 of the plasmon
generator 40. The metal film 401P is formed such that the top surfaces of
its portions lying on the second and third regions R2 and R3 are higher
in level than the top surface of the first metal portion 401 to be formed
later. Then, an etching mask (not illustrated) whose planar shape
corresponds to the planar shape of the first metal portion 401 is formed
on the metal film 401P. Next, portions of the adhesion layer 39 and the
metal film 401P other than their portions lying under the non-illustrated
etching mask are removed by RIE or IBE, for example. The non-illustrated
etching mask is then removed.

[0184] FIG. 24 shows the next step. In this step, first, a dielectric
layer of a dielectric material that is to form the
receiving-portion-forming layer 23 is formed over the entire top surface
of the stack. The metal layer 401P and the dielectric layer are then
polished by, for example, CMP, to the level of the top surface of the
first metal portion 401 (the top surface of the bonding portion 401B).
The dielectric layer thereby becomes the receiving-portion-forming layer
23. Further, the metal portion 401P thereby becomes the first metal
portion 401 to complete the first portion 41 of the plasmon generator 40
constituted of the main portion 401A of the first metal portion 401. In
FIG. 24, the boundary between the main portion 401A (the first portion
41) and the bonding portion 401B of the first metal portion 401 is
indicated in a dotted line.

[0185] FIG. 25 shows the next step. In this step, the multilayer film
portion 402 and the second metal portion 403 are formed on the first
metal portion 401 and the receiving-portion-forming layer 23. The
multilayer film portion 402 and the second metal portion 403 are formed
in the same manner as in the first embodiment. The second portion of the
plasmon generator 40 and the near-field light generator are thereby
completed. In FIG. 25, the boundary between the first portion 41 and the
second portion 42 of the plasmon generator 40 is indicated in a dotted
line.

[0186] As described above, the step of forming the plasmon generator 40 in
the method of manufacturing the near-field light generator according to
the present embodiment includes the step of forming the first portion 41
and the step of forming the second portion 42. The step of forming the
cladding includes the step of forming the receiving-portion-forming layer
23 that is performed simultaneously with the step of forming the first
portion 41.

[0187] The remainder of configuration, function and effects of the present
embodiment are similar to those of any of the first to third embodiments.

[0188] The present invention is not limited to the foregoing embodiments,
and various modifications may be made thereto. For example, as far as the
requirements of the appended claims are met, the shape of the plasmon
generator 40 and the locations of the plasmon generator 40, the core 20
and the main pole 29 are not limited to the respective examples
illustrated in the foregoing embodiments but can be chosen as desired.
For example, the plasmon generator 40 may be formed by stacking the
second portion 42 and the first portion 41 in this order from the bottom,
and the core 20 may be disposed above the first portion 41. In such a
case, the bottom surface of the main body portion 21 corresponds to the
"first surface" of the present invention, and the top surface of the main
body portion 21 corresponds to the "second surface" of the present
invention. The protruding portion 22 lies on the first region of the
bottom surface of the main body portion 21; the receiving-portion-forming
layer 23 lies on the third region of the bottom surface of the main body
portion 21; the protruding portion 22 and the receiving-portion-forming
layer 23 define therebetween a receiving portion; and at least part of
the first portion 41 is received in this receiving portion.

[0189] It is apparent that the present invention can be carried out in
various forms and modifications in the light of the foregoing
descriptions. Accordingly, within the scope of the following claims and
equivalents thereof, the present invention can be carried out in forms
other than the foregoing most preferable embodiments.